Re: Resample MHz signal

On Aug 20, 2:28 am, "Phil Allison" <philalli...@xxxxxxxxxx> wrote:
"James Barlow"

What I am really looking for is external hardware that will allow me
to upload an audio frequency WAV file, such a voice or music, from a
PC and then play it back at 100 times the original sample rate.

I'm guessing that you want to send the resulting signal through the
air. All the ultrasonic transducers I have read about have a resonant
point
and the frequency response drops either side of it. There are some
with -6dB points at around 50% and 150% of the resonant frequency
but I'm not aware of any with multi-octave response. Anyone?

Perhaps a combination of frequency shfiting and frequency
multiplication
might be more practical eg shift 300Hz-10000Hz to 40300-50000
then play back 44 times faster to get a signal about 400KHz wide
centred on 1.98MHz.

Perhaps do the frequency shift mathematically into a 192KHz PCM .wav
file then a DAC running at just over 8Msample/sec.

Getting data out of a PC that fast is not that easy. I'd be thinking
of
an ethernet device with some buffering but that's mainly because I
view low level drivers as a horrific thing to take on.

** Which will NOT be the case with a 100 times increase.

eg 50Hz x 100 = 5000 Hz = very audible.

Many audio applications can loose the bass without anyone caring.
The tiny loudspeakers in my laptop do nothing below 300Hz.

For voice you can get away with 300-3300hz though up to 8000hz
helps intelligabilty.

Frequency shifting the audio band up into the supersonic region is easily
possible with analogue circuitry

The simplist approch, mixing with 40Khz produces a voice signal
at 40300-43300 and an inverted voice signal at 39700-36400

An analog signal that avoids that seems to involve messing
with a multi-octave 90degree phas shifter.

Bob

.

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